1. Field of Invention
The present invention relates generally to an electrical connection box for use in a vehicle, e.g., a car. More particularly, this invention relates to an electrical connection box for use in a car that permits easy alteration of the construction of an existing internal circuit of a junction box and addition of a circuit to the existing internal circuit without changing the construction of the existing internal circuit of the junction box.
2. Description of Related Art
The same junction box as is used currently in one type of car is often applied to new cars which are to be manufactured by slightly changing the features of the original type of box. In adding a new system to an existing electrical system, it becomes necessary to take off a further power circuit from a circuit installed inside the junction box. In this case, the following two methods have hitherto been adopted.
In the first method, the construction of an internal circuit comprising a bus bar and installed inside the junction box is altered. In the second method, electrical wires of a circuit connected with the junction box are branched outside the junction box.
In the first method, in most cases, it is impossible to alter the internal circuit of the junction box because the junction box is designed with high density of its components. Even if space permits the alteration of the internal circuit, it may be necessary to add a bus bar to the existing internal circuit and alter the configuration of the junction box, which leads to a high manufacturing cost.
In the second method, it is necessary to increase the number of electrical wires of a wire harness in accordance with the added circuit and hence the diameter of the wire harness becomes larger, which makes it more difficult to wire the wire harness in a car body. That is, the wire harness cannot be inserted into a through-hole formed on the car body and interferes with other component parts. In addition, some electrical wires of the wire harness are required to be long, which leads to a higher manufacturing cost.
In order to solve the above-described problem, the assignees of the present inventor proposed a junction box that is disclosed in JP-A-5-22829 and corresponding U.S. Pat. No. 5,403,193 and shown in FIGS. 7A and 7B of the present application. This compact junction box 4 comprises a power source receiving/supplying socket 1, a power source supply connector 2 and an optional connection socket 3. The compact junction box 4 is removably connected to a power source receiving/supplying socket 6 of a junction box body 5 using the power source supply connector 2.
In this junction box, the addition of a system can be accomplished because it can be installed on the junction box body 5 without increasing the number of electrical wires of the wire harness. However, it is necessary to provide the junction box body 5 with the power source receiving/supplying socket 6 dedicated to an optional circuit, which makes the junction box body 5 large. Further, because the junction box 4 is provided with the power receiving/supplying socket 1 and the power source supply connector 2, the proposed junction box is comparatively large. Therefore, a considerable amount of space is required and hence, the compact junction box 4 cannot be installed on the junction box body 5 in many cases.